Integrated circuits have become ubiquitous in many portable electronic products, such as cell phones, portable computers, voice recorders, etc. as well as in many larger electronic systems, such as cars, planes, industrial control systems, etc. Across all applications, there continues to be demand for reducing the size and increasing performance of the devices.
Virtually all electronic products benefit from increasing functions and performance in integrated circuit chips while being designed into ever-smaller physical space. These demands are often very visible with the many consumer electronic products including but not limited to personal portable devices, such as cellular phones, digital cameras, and music players.
Thus, there is a constant drive within the semiconductor industry to reduce sizes as well as increase quality, reliability, and throughput of integrated circuit devices, e.g., microprocessors, memory devices, and the like. This drive is fueled by consumer demands for smaller, higher quality computers and electronic devices that operate more reliably.
These demands have resulted in continual improvement in the manufacture of semiconductor devices, e.g., transistors, as well as in the manufacture of integrated circuit devices incorporating such transistors. Additionally, reducing defects in the manufacture of the components of a typical transistor also lowers the overall cost per transistor as well as the cost of integrated circuit devices incorporating such transistors.
Among the parameters that would be useful to monitor and control are critical dimensions as well as overlay errors in photolithography. Critical dimensions are the smallest feature sizes that particular processing devices may be capable of producing. For example, the minimum widths of polysilicon or poly gate lines for metal-oxide semiconductor field-effect-transistors may correspond to one critical dimension for a semiconductor device having such transistors.
As the integrated circuit devices become smaller, so do the semiconductor critical dimensions for transistors, interconnect, or other features. The semiconductor critical dimensions have become so small that even very small offsets can represent a significant percentage of the semiconductor features resulting in a potentially large error.
Overlay errors including alignment and focus can affect these semiconductor features. In the case of multiple exposures, the critical dimensions can also be affecting by overlay errors. For example, during double exposure, the illumination energy dose can be reduced to approximately half and a misalignment or focus error can cause unintended or missing features.
Multiple exposure using customize illumination is one of the current resolution enhancement technique. Assist feature are placed in the orientation of the customized illumination. However, with double exposure, the energy dose per photomask exposure is half. The junctions, where the assist features intersect, are printed as a resist pillar on wafer. Reducing the size of the assist feature may affect the mask-making yield.
Despite the advantages of recent developments in integrated circuit fabrication there is a continuing need for improving manufacturing control, integrated circuit performance, photomask yield, and integrated circuit yield.
Thus, a need still remains for an integrated circuit system to provide improved control of manufacturing processes including photomasks. In view of the increasing demand for improved density of integrated circuits and particularly portable electronic products, it is increasingly critical that answers be found to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.